Variation and heritability of phenology in the fungus Monilinia vaccinii-corymbosi on blueberry

The germination of field-collected pseudosclerotia and the development of a pothecia from eight New Jersey populations of the mummy berry fungus Monili nia vaccinii-corymbosi were evaluated under controlled conditions in the gr eenhouse. Development data for apothecia were used to describe the timing o f apothecium formation and to estimate broad- and narrow-sense heritabiliti es of fungal phenology. Mean development times for the formation of apothec ia ranged from 35.4 to 54.7 days. The mean development times for population s collected from early-season cv. Weymouth ranged from 35.4 to 39.6 days an d were significantly shorter than the development times for three of the fo ur populations collected from late-season cv. Jersey (46.9 to 54.7 days) or for the population collected from mixed stands of cultivated blueberries ( 42.7 days). The development of populations from late cultivars planted in v ery close proximity to early cv. Weymouth was early (36.5 to 39.0 days) and not significantly different from the development of populations collected from cv. Weymouth. Phenotypic and genetic variances of apothecium developme nt for individual populations ranged from 18.9 to 44.8 and 7.2 to 30.9, res pectively. Broad-sense heritabilities of apothecia development for each fun gal population, calculated by partitioning phenotypic variation into geneti c and environmental components, ranged from 0.31 to 0.78. Narrow-sense heri tabilities of apothecia development, based on parent-offspring regression, ranged from 0.58 to 0.78. These results indicate that populations of M. vac cinii-corymbosi differ in phenology and that a significant portion of the p henological variation within populations is genetic. Thus, it is plausible to propose that the phenology of apothecium development is a component of f ungal fitness and that host phenology can influence the timing of pathogen development.